Two blasts that rocked Karachi last Friday left 140 people dead and over 500 injured as hundreds of thousands of people lined the streets to greet Bhutto, who flew in from Dubai after eight years of self-imposed exile.
Local media cited Bhutto's attorney, Farooq Naek, as saying that he had received a letter from an unidentified "leader of a group of al-Qaeda suicide bombers" threatening to slaughter the leader of the Pakistan People's Party (PPP) "like a goat."
Bhutto, who was unhurt in the Friday assassination attempt, earlier announced she suspected supporters of former military dictator General Zia-ul-Haq of orchestrating the attack. Zia, who overthrew Bhutto's father Prime Minister Zulfikar Ali Bhutto and had him executed in 1979, died in a car crash in 1988.
Bhutto, who said she had received death threats prior to her return to Pakistan, is set to run in the parliamentary elections slated for January next year. She pledged to put an end to extremism, and to develop democracy in the country if she returns to power.
Bhutto served as Pakistan's prime minister on two separate occasions, but both her previous governments were brought down amid corruption allegations and she was forced to flee in 1999, dismissing the allegations as politically motivated.
